1. Field of the Invention
The present invention relates to a jet-propulsion personal watercraft (PWC). More particularly, the present invention relates to a display device configured to display an operating state of the personal watercraft.
2. Description of the Related Art
In recent years, jet-propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft is equipped with an engine mounted within a space surrounded by a hull and a deck. The personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom surface of the hull and ejects it rearward from an outlet port of the water jet pump. As the resulting reaction, the personal watercraft is propelled forward.
The engine is provided with a number of sensors configured to detect an operating state of the engine, such as a crank position sensor configured to detect an engine speed of the engine, and a hydraulic-pressure sensor configured to detect a pressure of oil that circulates within the engine. The personal watercraft is equipped with an electric control unit (ECU) configured to control an operation of the engine. The ECU is electrically connected to the sensors. A signal detected by each of the sensors is transmitted to the ECU, and based on the signal, the ECU feedback-controls the operation of the engine.
In some personal watercraft, the ECU is configured to store data (information) associated with a drive state of the watercraft, which are represented by detection signals from the sensors, in a non-volatile memory such as an EEPROM (electrically erasable programmable read-only memory) or a flash memory built in the ECU. For example, Published Japanese Translation of PCT International Application, No. 2002-505725 (FIG. 1, pages 6 and 7) discloses an outboard engine, i.e., an engine externally mounted on a body of a boat, which is configured to store data such as an engine speed in an ECU equipped therein.
The above described data stored in the ECU is transferred to a computer which is, as desired, connected to the ECU. The transferred data is used to check a drive history of the watercraft, for the purpose of, for example, maintenance of the watercraft.
In order to feedback-control various operations of the engine based on the obtained data, the ECU must obtain detection signals from the sensors at relatively short sampling periods and carry out calculation for obtaining control information, using the detection signals. Therefore, when the detection signals from the sensors are written to memories built in the ECU concurrently with the feedback-control of the engine based on the obtained data, a load on a processing unit contained in the ECU increases.
In the configuration disclosed in the above described publication, during the operation of the engine, the obtained data are temporarily stored in a volatile memory such as a DRAM (dynamic random access memory) or a SRAM (static random access memory), and an electric power is supplied from a battery to the ECU for a certain time after the engine stops, to allow the data stored in the volatile memory to be re-written to the non-volatile memory. In general, since the time required to write data in the volatile memory is shorter than that in the non-volatile memory, the load on the processing unit can be reduced while the engine is subjected to the feedback-control, by writing the data in the volatile memory.
However, the ECU consumes a relatively large amount of electric power because of the presence of numerous electronic components mounted therein. And, the battery equipped in the personal watercraft is charged only when the engine is operating, and is not charged any more after the engine stops. Under this condition, if the ECU is energized with the engine in a stopped state, a relatively large amount of electric power is consumed in the battery, which may make it difficult for the engine to start up next.